What a flu shot does and doesn't do (and why most people should get one)

With 122 flu deaths so far this season, mostly among the elderly and with two of the victims being children, health advocates are doubling down on efforts to inform the public on the importance of the flu shot.

The main reason to get a flu shot is to help reduce transmission of the disease to those who are most vulnerable, according to various outlets. Many people do not get flu shots because they’ve gotten one in the past and still got the flu. While it is true that flu shots only prevent the flu about 60 percent of the time, the shots often alleviate symptoms of the flu even if the flu does develop. It also takes the shots about two weeks to become effective.

“Herd immunity” is the idea behind the flu shot. Those who are most likely to die from flu shots, such as the elderly, the very young or those who have reduced immune systems, come into contact with many different people who may be carriers. Each person who gets the shot further reduces the risk of transmitting the flu to someone else.

Many people who get sick after getting a flu shot assume the flu shot gave them the flu. According to the CDC, this is impossible. Those who get the flu after getting a flu shot would have gotten the flu anyway, and the flu shot might have reduced symptoms of that flu.

There are also some side effects may be mistaken for the flu. Some who get a flu shot experience low-grade fever, headache and muscle ache, but these tend to be less severe than the flu.

Medical professionals do say that those who have had sever allergic reactions to the flu shot in the past should not get it again, however. There is also a rare condition called Guillain-Barré Syndrome which causes the immune system to attack the nerves. Symptoms of this syndrome include difficulty with eye or facial movements, speaking, chewing or swallowing, severe cramp-like pain, rapid heart rate and other symptoms. This is a rare issue with fewer than 20,000 cases in the United States per year, but anyone who has this syndrome should also not get the flu shot.

But those who have never had any reaction to the flu shot are encouraged to get it, even if they are not afraid of the flu or have never had it. Often people do have the flu, but their bodies handle it so well that the symptoms seem like something mild. These people can still transmit the flu to people whose immune systems are not as strong, and are encouraged to get the shot to prevent that from happening.